一、问题
将字符串 "PAYPALISHIRING" 以Z字形排列成给定的行数: P A H N A P L S I I G Y I R 之后从左往右,逐行读取字符: "PAHNAPLSIIGYIR" 实现一个将字符串进行指定行数变换的函数: string convert(string s, int numRows); 示例 1: 输入: s = "PAYPALISHIRING", numRows = 3 输出: "PAHNAPLSIIGYIR" 示例 2: 输入: s = "PAYPALISHIRING", numRows = 4 输出: "PINALSIGYAHRPI" 解释: P I N A L S I G Y A H R P I
二、解决
class Solution { public String convert(String s, int numRows) { if (numRows == 1) return s; List<StringBuilder> rows = new ArrayList<>(); for (int i = 0; i < Math.min(numRows, s.length()); i++) rows.add(new StringBuilder()); int curRow = 0; boolean goingDown = false; for (char c : s.toCharArray()) { rows.get(curRow).append(c); if (curRow == 0 || curRow == numRows - 1) goingDown = !goingDown; curRow += goingDown ? 1 : -1; } StringBuilder ret = new StringBuilder(); for (StringBuilder row : rows) ret.append(row); return ret.toString(); } }